Merkel cell carcinoma (MCC) is an aggressive, polyomavirus-associated skin cancer with reported incidence that has quadrupled in 20 years and 5-year disease-associated mortality of over 40%. Despite its growing health impact, very few clinical trials have focused on this disease. The Merkel cell polyomavirus (MCPyV), discovered in 2008, is involved in the pathogenesis of approximately 80% of MCC tumors. Several lines of evidence suggest the importance of immune function in MCC. The viral dependence of MCC, combined with important recent insights into the reversibility of its immune evasion mechanisms, present exciting opportunities to develop rational therapy for this often-lethal cancer. A uniquely strong set of clinically annotated MCC specimens and established multi-disciplinary collaborations have allowed rapid translation of immune observations to in vivo application. Using support from the K24 in the prior period, we have secured two new R01 grants to carry out three funded Aims: Aim 1) Determine whether a serologic test for MCPyV has clinical utility, Aim 2) Map MCPyV-specific T-cell epitopes and create tools to isolate, characterize and augment the cellular immune response, and Aim 3) In a phase I/II trial, evaluate the combination of polyclonal virus-specific adoptive T cell therapy along with HLA-upregulating adjuvants in 16 MCC patients. Three additional Aims, currently un-funded, would also be supported by this K24: Aim 4) Determine the prevalence, prognostic and therapeutic significance of Merkel polyomavirus-negative MCC tumors, Aim 5) Develop the next AJCC staging system and therapeutic guidelines for MCC using multiinstitutional and national registry datasets, Aim 6) Determine the efficacy of PD1 therapy in metastatic Merkel cell carcinoma in a multi-center clinical trial in collaboration with the Cancer Immunotherapy Trials Network. Since the start of the K24, Dr. Nghiem has mentored 49 trainees (41 of whom were directly involved in research with Dr. Nghiem) in diverse disciplines at all levels up to Assistant Professor. 40 of 41 mentees (98%) were involved in patient-oriented research. Of the 41 trainees involved in research with Dr. Nghiem since the start of the K24, 16 mentees currently hold faculty positions, and an additional 22 remain in clinical or patient- oriented research training. 32 of these 41 mentees have at least one publication with Dr. Nghiem. Currently, Dr. Nghiem mentors 15 research trainees in the career categories that are the major focus of the K24 mechanism: 3 junior clinical faculty, 3 fellows, 4 clinical residents, and 5 graduate/MD-PhD students. During the current funding period (2009 - present), 27 original research studies have been published, all of which relate to the aims of the K24 and 26 of which are co-authored with one or more mentees. Currently, 65% of Dr. Nghiem's effort is devoted to mentoring and patient-oriented research funded by the K24 and by two MCC- related R01s that arose from seed projects funded by the K24. The 20% effort he now devotes to clinical and administrative responsibilities would need to expand significantly if not for support from the K24.